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arXiv · 2104.09236

Stoichiometric Tuning of Lattice Flexibility and Na Diffusion in NaAlSiO4: Quasielastic Neutron Scattering Experiment and Ab-initio Molecular Dynamics Simulations

Mayanak K. Gupta·Ranjan Mittal·Sajan Kumar·Baltej Singh·Niina H Jalarvo Olivier Delaire·Rakesh Shukla·Srungarpu N. Achary·Alexander I. Kolesnikov·Avesh K. Tyagi·Samrath L. Chaplot
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Abstract

We have performed quasielastic neutron scattering (QENS) experiments up to 1243 K and ab-initio molecular dynamics (AIMD) simulations to investigate the Na diffusion in various phases of NaAlSiO4 (NASO), namely, low-carnegieite (L-NASO; trigonal), high-carnegieite (H-NASO; cubic) and nepheline (N-NASO; hexagonal) phases. The QENS measurements reveal Na ions localized diffusion behavior in L-NASO and N-NASO, but long-range diffusion behavior in H-NASO. The AIMD simulation supplemented the QENS measurements and showed that excess Na ions in H-NASO enhance the host network flexibility and activate the AlO4/SiO4 tetrahedra rotational modes. These framework modes enable the long-range diffusion of Na across a pathway of interstitial sites. The simulations also show Na diffusion in Na-deficient N-NASO through vacant Na sites along the hexagonal c-axis.

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Mayanak K. Gupta, Ranjan Mittal, Sajan Kumar, Baltej Singh, Niina H Jalarvo Olivier Delaire, Rakesh Shukla, Srungarpu N. Achary, Alexander I. Kolesnikov, Avesh K. Tyagi, Samrath L. Chaplot. 2021-04-19. Stoichiometric Tuning of Lattice Flexibility and Na Diffusion in NaAlSiO4: Quasielastic Neutron Scattering Experiment and Ab-initio Molecular Dynamics Simulations. https://arxiv.org/abs/2104.09236

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